Kinetic Finger

thingiverse

In May 2015, I embarked on a groundbreaking challenge to create a fully functional finger prosthetic that would not only revolutionize the field but also make it accessible to anyone on the planet - for free. The "Kinetic Finger" is a body-powered device featuring no complicated moving parts and utilizing TPE flexible hinges to allow the finger to open and close in a remarkably realistic manner. Its design is sleek and unobtrusive, making the "Kinetic Finger" suitable for use under work gloves. During testing, finger amputees were able to effortlessly pick and place a wide variety of heavy and light objects, as well as play a piano and finger pick a guitar with remarkable dexterity. The "Kinetic Finger" is designed to resemble an accessory, similar to a watch, that can be attached and removed at the user's convenience. This project is an ongoing work in progress, so files will be updated regularly. I invite you to share your experiences and trials to help me continuously improve this design. Feel free to e-mail me at matbowtell@gmail.com with any questions or feedback. Please see the videos attached for a demonstration of the "Kinetic Finger". This design is intended for evaluation purposes only, and I assume no responsibility for any accidents or claims resulting from making or distributing this design. Thank you. Print Settings Printer: Flashforge Creator Pro Rafts: No Supports: No Resolution: 0.2mm Infill: 40% Notes: (1) PLA Parts: 40% infill, one perimeter, 0.2mm layer height, no supports, no raft, 60mm/sec at 215C. Proximal phalanx, middle phalanx, distal phalanx, tensioner clip (4 parts) (2) Ninjaflex (flexible and elastic TPE) Parts: 100% infill, one perimeter, 0.2mm layer height, supports, no raft, 30mm/sec at 230C. Distal inter-phalangeal hinge, proximal inter-phalangeal hinge, tendon guide (3 parts) (3) Ninjaflex (flexible and elastic TPE) Parts: 30~50% infill, one perimeter, 0.2mm layer height, no supports, no raft, 30mm/sec at 230C. Distal phalanx grip, middle phalanx grip (2 parts) All parts should be scaled except for the tendon guide and tensioner clip. Recommended tendon: 50lb (25kg) braided fishing line. Recommended Velcro for tensioner clip: double-sided 25mm width, 400mm length. Recommended adhesive: Superglue for tendon and holding grips in place. Scaling and assembly instructions to come soon. Index finger test case: 100% scale Ring finger test case: 90% scale Post-Printing Design merits I would like to share with you the key merits of this design, hoping that some of you may find them useful for improving your own designs. 1) Hinges. The flexible hinges have been designed in a "U" shaped configuration to prevent them from flopping around the center point and give improved spring-back. The center is also cut out to prevent the hinge from sliding out during operation. They are fitted from one side, and then stretched to fit from the other side. The hinges have a dampener which forms a part of the knuckle. There are two reasons for this: The first reason is to allow for silent operation with no contact of plastic parts. The second reason is to fill the gap when opened to allow gloves to be worn without getting caught in the void. 2) Joints: Having the center available in the joint allows the tendon hole to come as far forward and as close to the hinge as possible, requiring less retraction of the tendon to close the finger. Bringing the tendon guide hole as far forward as possible also allows the cavity for the finger to come very close to the joint, allowing for realistic finger length when the finger is severed close to the joint. 3) Tendon guide: The flexible tendon guide is comfortable and flexes with the hand. It does not bear the load of the tendon; rather, it is only a guide to the rigid tensioner clip. The rigid tensioner clip takes the full load of the tendon and is fixed to the wrist by a Velcro strap. Therefore, there is no stretching of the flexible tendon guide which improves grip strength. 4) Grips: The grips are also printed in flexible material and provide more grip than plastic. I have also made a scalable mold for super grippy silicone tips which will be uploaded shortly. The grips have key-ways to assist in adhesion when glued into place.